1. Field of the Invention
The present invention relates to structured data classifying devices which retrieve and classifying structured data and more particularly to a structured data classification device capable of easily classifying structured data in accordance with the purpose of a user.
2. Description of the Related Art
As a device for storing, classifying and arranging a large amount of electronic documents, file systems and document data bases are known at present and used in many offices. In this connection, FIG. 21 shows an example of a classification structure which is created by arranging documents with a certain classification standard. The classification standard in this example comprises a classification for a large group which is, for example, "kind of documents" such as "monthly journal", "report" or "order document", and a classification for a small group which is, for example, "creation date of a document" such as "month and year" In this classification structure, the large-group classification, "kind of documents", is immediately subordinate to a "root", the smaller classification, "creation date of a document" is immediately subordinate to "kind of documents", and actual documents are immediately subordinate to "creation date of a document".
When it is desired to search documents for each "creation date of a document",it is necessary to search all of the documents for each "kind of documents For example, referring to FIG. 21, in order to search all documents classified as "January, 1991",it is necessary to search documents classified as "January 1991" in the small-group classification 2110A, 2120A, and 2130A respectively subordinate to "monthly journal" 2110, "report" 2120 and "order document" 2130. When it is desired to search documents for a new classification standard such as "author",it is necessary for all the documents to be search and to be re-classified.
In document databases and electronic filing systems, there is provided an area in which keywords or attributes can be written in documents. By using the keywords or attributes, it is possible to retrieve documents and to pick up only desired documents by using retrieval query.
Known other similar devices are disclosed in Japanese Patent Laid-open Applications Sho 63-157229 and Hei 1-189721.
The Laid-open Application Sho 63-157729 discloses a device which re-displays documents, as if they were re-classified, by selecting a classification from a plurality of predetermined classifications, using attributes and keywords. The Laid-open Application Hei 1-189721 discloses a device which selects some of beforehand prepared classification axes to thereby display the position of a desired document in the manner of multi-dimensional display.
However,the conventional document databases and electronic filing systems including the devices disclosed in these Japanese Laid-open Application have the following problems:
(1) Attributes or keywords must be added to documents. It requires a great amount of time and labor to add attributes or keywords to documents. It is not possible to re-classify the documents without addition of attributes or keywords. PA1 (2) Although documents are updated, attributes and keywords are not automatically updated because the contents and attributes of a document are separately managed. A known method to avoid this problem is the retrieval over the whole document and extraction of keywords. In this method, however, unintended documents are also retrieved, causing the loss of time. As the number of unintended documents increases, time and labor for retrieval increase. PA1 (3) The retrieval query must be rewritten many times. Conditional retrieval is employed when the attribute values and keywords are clear. However, when a target document cannot be identified by its attributes or keywords, or when the retrieval is for the first time, the attribute values and range of the retrieval query are likely to be changed in trial and error manner. Thus, the retrieval query must be rewritten many times, which requires a large amount of work and time. PA1 (4) Maintaining classification according to classification items requires a large amount of work. Maintenance of classification items to classify/arrange documents is left to the user. For example, when the "reports for January 1991" are to be searched in a structure shown in FIG. 22, only a person who stored the document can know which of "January 1991" at 2210 and "report" at 2220 should be searched. It is possible to store a document at a place which is not related to that document. A large amount of work is required for maintaining the documents. PA1 (5) It requires a large amount of work to classify documents beforehand. In the devices disclosed in the Japanese Applications Sho 63-157229 and Hei 1-189721, the classification items could be replaced to "kind of documents" and "creation date" To this end, all the documents must be classified beforehand with every possible classification items.